Heretofore, internal combustion engines have been manufactured based on a constant speed/fixed volume design in that the engine speed in revolutions per minute (RPM) and piston displacement are the major factors in determining horsepower and torque delivered at the flywheel. The final delivered horsepower/torque requirement necessary for a particular application is established to satisfy anticipated road load conditions consisting of (a) rolling resistance, (b) air resistance, (c) vehicular gross weight and (d) road grade.
Road Horsepower is expressed by the formula: ##EQU1## Where: Cr=Coefficient of Rolling Resistance
Ca=Coefficient of Air Resistance PA1 V=Vehicle speed, MPH PA1 A=Frontal area in square feet PA1 W=Gross Weight in pounds PA1 G=Road Grade, percent PA1 First, the designer/manufacturer will no longer be required to make assumptions during design of a specific engine to cover all possible driving conditions in a single block multi-cylinder engine and arrive at a single optimal horsepower curve. Instead this invention affords the availability of two or more specific horsepower/torque curves at the flywheel to economically adapt to a variety of road and driving conditions. PA1 Second, the invention will substantially reduce the amount of hydrocarbon emissions in the exhaust due to wall quenching during cold starts and normal operating conditions. PA1 Third, the invention will drastically reduce hydrocarbon and nitrogen oxide emissions together therefor decreasing smog products. PA1 Fourth, the invention will provide improved economic use of petroleum base fuels increasing the mileage (MPG) due to the flexibility of allowing the operator to select the engine volume required to meet specific conditions re: gross-load, heavy traffic, idling, cruising speeds, road grade and air resistance.
Predicated on the assumed requirements, a final design for a specific single block of four, six, eight or more cylinders is produced for installation in a variety of production type vehicles. Since the engine design and selection is based on a variety of assumed conditions, it is in most cases oversized for the greater percentage of use normally encountered.
Air pollution contributed by vehicle emissions includes Hydrocarbons (HC), Carbon Monoxide (CO), Oxides of Nitrogen (NO), Oxides of Sulfur (SO2) and Particulate Matter. Of the total Hydrocarbon Emissions from uncontrolled vehicle engines, 20 to 25 percent is caused by crankcase blow-by, 60 percent of the undesirable exhaust emissions are formed mainly within the combustion chamber of the engine during or after the combustion process and appear in the exhaust. The remainder of the emissions are contributed to evaporative losses.
In a four cycle, water cooled engine "wall quenching" is the predominate source of exhaust hydrocarbons. Wall quenching is a combustion phenomena that arises when a flame attempts to propagate in the vicinity of a surface or wall. Normally the effect of the wall is a slowing down or stopping of the reaction. In general, wall quenching results from both the chain breaking of the chemical reactions of the fuel/air mixture and from the cooling of the layer of charge adjacent to the wall (which is cooler than the rest of the combustion chamber). As a result the flame will not propagate completely to the wall surface. Wall quenching is the principal source of unburned hydrocarbons in the exhaust of an engine under most normal conditions and is extremely high during cold start conditions.
Of course hydrocarbons present a serious environmental concern. At a level of 0.15 parts per million (ppm) oxidant, approximately 50 percent of the population experience some eye watering. Further, a reduction of nitrogen oxide first increases then decreases smog products; therefore, nitrogen oxide and hydrocarbons together should be reduced to virtually zero before a smog benefit is realized.
To date state of the art engines are fixed volume in design. Due to the single block multi-cylinder vehicle engines presently in use, petroleum base fuels are used uneconomically during periods of cold starting, heavy traffic (when engine idling and extremely slow speeds are encountered) and at cruising speeds when road conditions, rolling resistance, air resistance and grade do not require full design horsepower. In recent years due to Federal mandates, automotive manufacturers have developed and placed in use a variety of emission control systems. These systems along with the electronic ignition, fuel injection and the use of unleaded fuel have contributed greatly to the decrease of exhaust and evaporative emissions, but have not reached the emission standard goals projected for the future. Also, these emission control systems, which are add-on in nature, have further contributed to the inefficient use of gasoline fuels.
Based on information available in the "1991 Gas Mileage Guide, EPA Fuel Economy Estimates, October 1990, DOE/CE-0019/10", the average mileage (miles per gallon) for passenger type automobiles manufactured in the United States is 18.14 MPG city and 24.64 MPG highway. The current practice within the automotive manufacturing industry of utilizing a single block multi-cylinder engine based on the constant speed/fixed volume concept continues to contribute now and into the future to excessive air pollution and the inefficient use of petroleum base fuels.